In semiconductor fabrication, it is important to report on the performance of semiconductor fabrication tools in the various production processes. Systems for measuring tool performance typically receive as their input status data of respective tools, i.e. up or down status of the tool, production wafer output data, and data on the amount of wafers queuing and queuing time at the respective tools. The system processes the input data and typically outputs a number of performance evaluation charts, which in turn are used to identify potential performance problems, and generally in deciding various operating and production parameters in a semiconductor fabrication plant.
The charts typically include reports on actual wafer output, amount of queuing wafers and queuing time, tool ability or up time in percentage, and the efficiency of tools, each against time, typically in daily or weekly resolution. The charts can be provided for individual tools or for groups of tools associated with respective production processes in the plant. The information provided by the systems for measuring tool performance facilitates operation of the plant, e.g. a sudden surge in the amount of wafers queuing at a particular tool can indicate that the relevant tool is not performing, which in turn can lead to a loss in utilization of a bottleneck tool downstream from the effected tool. Another example is the information from uptime reports, i.e. reports on the tool availability for production as a percentage, where poor uptime is often responsible for poor overall tool performances. As another example, reports on the tool efficiency facilitates an assessment whether a tool is being fully utilized in a best possible way.
Amongst the different tools in a semiconductor fabrication plant, performance measurements of multi-path cluster tools have typically been performed based on an averaging analysis. Multi-path cluster tools are tools which consist of a number of production chambers or modules and interconnecting wafer conveyancing systems between the chambers or modules, and between load locks at the input and output stages. In multi-path cluster tools, wafers proceed on different Intended Process Paths (IPPs), in a parallel-series sequence of the respective modules or chambers.
One example of a multi-path cluster tool is a Metal Sputtering Tool (ATM) tool. For the ATM tool, Ti-pasting, which is a particle improvement activity, involves only two out of four available chambers within the tool. Inaccuracies arise in measuring tool performance using the average of the individual performance of the chambers. More particular, during Ti-pasting, the averaging method yields a 50% uptime for the multi-path cluster tool, with two out of four available chambers running, but practically all of the chambers, and therefore the multi-path cluster tool, are not available for production. Therefore, the performance measurement system analyses the tool based on an inaccurate, i.e. longer uptime, which in turn yields e.g. in a lower efficiency measurement for that tool, where the uptime is linked to the actual wafer output data for that tool.
To address this problem, in a modified existing performance measurement system and method, a simple truth table has been incorporated. More particular, the truth table is utilized to classify different combinations of status data for the respective chambers or modules of the multi-path cluster tool into a binary status for each IPP of the multi-path cluster tool. In other words, a knowledge based classification or truth table is utilized to identify an up or down status for each IPP of the multi-path cluster tool, and the overall performance of the multi-path cluster tool, in particular its overall operational uptime, is then calculated based on the binary status data for each IPP over respective operation time periods.
It has been recognized by the inventors that such modified performance measurement systems and methods can still result in inaccurate performance measurements for multi-path cluster tools. In particular, the binary status data obtained utilizing the classification or truth table does not account for non-binary characteristics of multi-path cluster tools recognized by the inventors.
A need therefore exists to provide a system and method for measuring tool performance of a multi-path cluster semiconductor fabrication tool that seeks to address the problem recognized by the inventors.